Meta-analysis of plasma to red blood cell ratios and mortality in massive blood transfusions for trauma

Background: The current military paradigm for blood transfusion in major trauma favours high plasma:RBC ratios. This study aimed determine whether high plasma: red blood cell (RBC) ratios during massive transfusion for trauma decrease mortality, using meta-analysis of contemporaneous groups matched for injury severity score. Methods: A systemic review of the published literature for massive blood transfusions in trauma was performed. Patients were categorised into groups based on plasma: RBC transfusion ratios. Meta-analysis was only performed when there were no significant differences in Injury Severity Score (ISS) between ratio groups within studies. The main endpoint was 30-day mortality. Results: Six observational studies reporting outcomes for 1885 patients were included in this meta-analysis. Five studies were from civilian environments and one from a military setting. Ratio cut-offs at 1: 2 were the most commonly reported, demonstrating a survival advantage with higher ratios (OR 0.49, 95% CI 0.31-0.80, p = 0.004). Ratios >= 1: 2 showed a significant reduction in mortality compared to lower ratios (OR 0.56, 95% CI 0.40-0.78, p < 0.001). Reducing the cut-off level was still protective ( ratios between 1: 2.5 and 1: 4, OR 0.41), although the confidence interval was wide (0.16-1.00, p = 0.05) and data heterogenous (I-2 = 78%). Ratios of 1: 1 were not proven to confer additional benefit beyond ratios of 1: 2 (OR 0.50, 95% CI 0.37-0.68, p < 0.001). Conclusions: In groups matched for ISS, there was a survival benefit with high plasma: RBC resuscitation ratios. No additional benefits of 1: 1 over 1: 2 ratios were identified. (C) 2012 Published by Elsevier Ltd.